Not the creator, but:
1) Once you pay the money, it's yours entirely, maybe some minor VAT or other taxes, but you don't have to pay anything else.
2) Winrar is an application that you can purchase. It allows you to extract compressed and zipped folders, which you can use to download most games, applications etc. legally (and illegally, if you want to). It costs like 20 to 30 dollars, but again when you buy it, it's yours forever.
3) It should work as long as you transfer all the save files from the old version to the new version. Otherwise, if you're playing the same version it always works guaranteed.
Hope it helps!